For most large turbine engine applications, there are certainly some constraints on engine diameter as it relates to the impact on combustor performance. But the combustion volume is usually quite sufficient to accommodate the overall performance objectives for a particular application. As a result, the turbine engine can in most cases be designed to provide the volume for combustion that is required to achieve the desired performance objectives.
On the other hand, it is quite well known that small thrust turbine engines present a myriad of rather serious design problems. Almost always, there are restrictions on overall engine diameter which, in turn, has a significant impact on achieving performance goals inasmuch as the dome height of a given combustor is usually tied very directly to engine diameter. Because of this limitation, the dome height has often been much less than satisfactory and combustor loadings are often much greater than desired.
Generally speaking, the dome height is determined by the difference between the radius of the engine and the radius of the exhaust duct. The exhaust duct, which typically extends between the turbine wheel and the turbine nozzle located axially downstream of the combustor, is usually of substantially uniform diameter corresponding rather directly to the diameter of the turbine wheel at the point where the gases of combustion exit the turbine wheel en route to the turbine nozzle. Because of this arrangement, the dome height cannot be varied to any significant degree to achieve an increased combustion volume.
As a result, the only other possibility for increasing combustion volume is increasing combustor length. However, this may also be undesirable for a number of reasons including space availability for the turbine engine and the impact of such relative length in relation to dome height on overall performance. For these reasons, there has been a significant awareness of the need to increase the combustion volume in the constraints of the same engine envelope.
The present invention is directed to overcoming one or more of the foregoing problems and achieving one or more of the resulting objects.